Data storage device, such as solid state drive (SSD), secure digital (SD) memory card or portable flash memory, mainly is constituted by a control unit and a data storage medium. And the data storage medium is constituted by a plurality of columns for storing data.
Inevitably, secondary products may be produced in the manufacturing process of data storage devices. Therefore, it is necessary to screen all the bad columns in the data storage medium and record the bad columns in a bad column summary table before shipping the secondary products to market. According to the bad column summary table, the control unit is prevented from accessing these bad columns so as to avoid data access error during operation.
In general, data storage device uses error correcting code (ECC) to correct its stored data. However, the conventional method for screening bad columns may not only waste a lot of usable storage space but also result in data storage or correction problems due to the low effectiveness of reducing the number of bad columns.